Regulating valves of the generic type are known in particular at steam turbines. If such regulating valves are operated for example in a throttled operating state, that is to say in a not fully open or closed operating state of the regulating valve, a characteristic flow pattern, which is substantially characterized by the formation of a wall-jet region with flow speeds which are considerably higher than the flow speeds of a core-flow region of a volume flow, virtually always forms in a flow interior space of the regulating valve.
In this respect, the differing flow speeds give rise to a shear layer between the wall-jet region of the volume flow flowing through the regulating valve and the core-flow region of this volume flow, with often non-negligible, high speed gradients.
It is known both from experimental and from numerical studies of the flow behavior at such regulating valves that, in the shear layer, flow instabilities can occur which can give rise to critical resonance effects in the flow space of the regulating valve. In the worst case, this can lead to an excitation of the regulating valve structure of such an undesirable nature that it is capable of bringing about damage to said regulating valve structure.
In order to counteract said resonance effects, it is known to provide flow straighteners in the region of the valve seat on the valve housing, which straighteners can contribute to a positive influence on the shear layer. However, said fixtures in the form of flow straighteners lead nearly always to considerable flow losses, as a result of which the total power of the turbine or steam turbine is lowered.
U.S. Pat. No. 5,150,736 discloses a valve which has a cylindrical valve shut-off member and an annular valve seat.